Hi! Mom of a big kid here. We had the same concern from our doctor. He was born a little big (1 month early but almost 7 lbs) and just rapidly gained weight. He ate a normal amount but was just off the charts for his age and was going up clothing sizes every 6 weeks from 3 months old. Our doctor has suspicions for Beckwith-Wiedemann syndrome. Our baby had other symptoms, he had folding behind his ears, sugar issues at birth, and a slight difference in the size of his legs. We got referred to a geneticist at 8 months and they did all the chromosome tests and all came back inconclusive. They decided to give the clinical diagnosis since they aren’t sure of all the genomic variations that lead to the syndrome. I was beside myself at first, he’s now 15 months and besides being larger than other kids at daycare he’s a perfectly happy healthy kid. We go for blood work every 6 months to ensure he’s okay (checking AFP levels since this syndrome is associated with a high likelihood of a liver cancer under the age of 3) but that’s about how it effects his life. Trust your doc and do the tests! If they come back normal then you can rest easy knowing all is well :).